U.S. patent application number 11/044797 was filed with the patent office on 2006-07-27 for single wire interface providing analog and digital communication between an ac power adapter and an electronic device.
This patent application is currently assigned to TEXAS INSTRUMENTS INCORPORATED. Invention is credited to Garry Ross Elder, Jose Antonio Vieira Formenti.
Application Number | 20060164061 11/044797 |
Document ID | / |
Family ID | 36696101 |
Filed Date | 2006-07-27 |
United States Patent
Application |
20060164061 |
Kind Code |
A1 |
Formenti; Jose Antonio Vieira ;
et al. |
July 27, 2006 |
Single wire interface providing analog and digital communication
between an AC power adapter and an electronic device
Abstract
A single wire interface between an AC power adapter and end
equipment, such as a notebook computer, conveys digital information
from the adapter to the end equipment when the adapter is operative
in a first operating mode and carries an analog signal employed in
a closed loop to control the DC output voltage of the AC power
adapter when the AC adapter is operative in a second operating
mode. When the AC adapter is operative in the first operating mode,
the AC adapter output voltage is clamped to a first predetermined
voltage and when the AC adapter is operative in the second
operating mode the output voltage is clamped to a second
predetermined voltage, wherein the first predetermined voltage is
less than the second predetermined voltage. Mechanisms for
switching between the first and second operating modes are also
provided.
Inventors: |
Formenti; Jose Antonio Vieira;
(Allen, TX) ; Elder; Garry Ross; (Spratton,
GB) |
Correspondence
Address: |
TEXAS INSTRUMENTS INCORPORATED
P O BOX 655474, M/S 3999
DALLAS
TX
75265
US
|
Assignee: |
TEXAS INSTRUMENTS
INCORPORATED
|
Family ID: |
36696101 |
Appl. No.: |
11/044797 |
Filed: |
January 27, 2005 |
Current U.S.
Class: |
323/371 |
Current CPC
Class: |
H02J 7/022 20130101;
H02J 2207/20 20200101; H02J 7/02 20130101 |
Class at
Publication: |
323/371 |
International
Class: |
F02P 3/02 20060101
F02P003/02 |
Claims
1. An AC power adapter for providing a DC output voltage for
powering an electronic device, said AC power adapter comprising: a
communication engine for serially communicating digital information
over a single wire interface for receipt by a host in an electronic
device and receiving digital information over said single wire
interface from said host; interface circuitry for conveying an
analog control signal over said single wire interface to control
said DC output voltage; and control circuitry operative to select
between a first operating mode in which said communication engine
utilizes said single wire interface and a second operating mode in
which said interface circuitry utilizes said single wire
interface.
2. The adapter of claim 1 wherein said control circuitry is
operative to select said first operating mode upon power up of the
adapter.
3. The adapter of claim 1 wherein said communication engine is
operative in response to receipt of a first predetermined
communication from said host to transmit digital information over
said single wire interface for receipt by said host.
4. The adapter of claim 3 further including at least one memory for
storing said digital information, wherein said communication engine
is operative to retrieve said digital information from said
memory.
5. The adapter of claim 3 wherein said digital information
transmitted over said single wire interface comprises information
pertaining to said AC power adapter.
6. The adapter of claim 5 wherein said information pertaining to
said AC power adapter comprises data identifying said AC power
adapter.
7. The adapter of claim 5 wherein said information pertaining to
said AC power adapter comprises data identifying a maximum output
voltage of said AC power adapter.
8. The adapter of claim 3 wherein said communication engine is
operative in response to receipt of a second predetermined
communication from said host to generate a first control signal and
said control circuitry is operative in response to said first
control signal to select said second operating mode.
9. The adapter of claim 1 wherein said control circuitry is further
operative to set the output voltage of said AC power adapter at a
first predetermined output voltage in said second operating mode
and is operative to set the output voltage of said AC power adapter
to a second predetermined output voltage in said first operating
mode, wherein said second predetermined output voltage is less than
said first predetermined output voltage.
10. In a system including an AC power adapter producing a DC output
voltage for powering an electronic device, a method for controlling
said AC power adapter comprising: selecting within said AC power
adapter between a first operating mode and a second operating mode;
in said first operating mode, transmitting digital information to
said electronic device and receiving digital information from said
electronic device over a single interface wire coupling said AC
power adapter and said electronic device; and in said second
operating mode transmitting an analog control signal over said
single interface wire and controlling said DC output voltage of
said AC power adapter based at least in part on said analog control
signal.
11. The method of claim 10 wherein said analog control signal
comprises a current.
12. The method of claim 11 further including the step of generating
said current using current sink control logic controlling a current
sink within said electronic device.
13. The method of claim 10 further including selecting said first
operating mode in response to power up of said adapter.
14. The method of claim 10 further including: transmitting digital
information over said single wire interface from a communication
engine in said adapter for receipt by said electronic device;
receiving at said communication engine a first predetermined
communication from said electronic device over said single wire
interface; and in response to the receipt of said first
predetermined communication, changing from said first operating
mode to said second operating mode.
15. The method of claim 14 further including the step of
transitioning said AC power adapter from said second operating mode
to said first operating mode in the event said analog control
signal has an amplitude that exceeds a first analog threshold.
16. The method of claim 14 further including the step of
transitioning said AC power adapter from said second operating mode
to said first operating mode in the event said analog control
signal has an amplitude less than a second analog threshold.
17. The method of claim 14 further including prior to said
transmitting step, the step of retrieving said digital information
from said memory.
18. The method of claim 14 wherein said transmitting step comprises
the step of transmitting digital information pertaining to at least
one characteristic of said AC power adapter.
19. The method of claim 14 wherein said transmitting step comprises
the step of transmitting digital information that specifies a
maximum output voltage of said AC power adapter.
20. The method of claim 14 wherein said transmitting step comprises
the step of transmitting digital information that identifies said
AC power adapter.
21. The method of claim 10 further including the steps of:
controlling said DC output voltage of said AC power adapter to
assume a first predetermined voltage when said first operational
mode is selected; and controlling said DC output voltage of said AC
power adapter to assume a second predetermined voltage when said
second operating mode is selected, wherein said first predetermined
voltage is less than said second predetermined voltage.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] Not Applicable
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not Applicable
BACKGROUND OF THE INVENTION
[0003] The present application relates to AC power adapters for
powering electronic equipment such as notebook computers, and more
specifically, to AC power adapters employed with battery powered
electronic equipment such as notebook computers.
[0004] The use of AC power adapters to power portable electronic
equipment is well known. AC power adapters are known that employ
switching converters to produce a DC adapter output voltage. It is
understood that when an AC adapter applies an output voltage to the
powered electronic equipment in excess of an acceptable voltage
limit, the circuitry in the electronic equipment may be
damaged.
[0005] Typical AC adapters produce a fixed output voltage from AC
power. The end equipment being powered commonly includes a linear
stage or a switching mode DC to DC converter that is employed to
implement battery charger functions in battery powered systems.
Control loops that are used to assure that proper voltages are
applied to recharge batteries and to power the end equipment are
typically provided in the end equipment. The inclusion of such DC
to DC converters and associated control loops in the end equipment
has a number of disadvantages. The components associated with the
DC to DC converters and/or the linear stage power components add
undesirable heat and weight to the end equipment. This is
particularly undesirable in notebook computers where there is an
ever increasing desire to produce smaller and lighter products.
[0006] When powering and recharging batteries in end equipment via
an AC adapter, the AC adapter usually has a module that contains
the adapter circuitry. A power cord connects the module to AC line
power and another interface cable connects the AC adapter to the
end equipment. It is desirable for the interface cable to be
flexible for ease of use and it is also desirable for the AC
adapter to be of light weight since, as in the case of notebook
computers, it is often transported with the equipment.
[0007] For these reasons, an improved system and method for
interfacing an AC adapter to battery operated electronic equipment
that avoids the above-identified disadvantages of known AC
adapters-end equipment interfaces would be desirable.
BRIEF SUMMARY OF THE INVENTION
[0008] In a system including an AC adapter and an electronic device
which is optionally powered by a battery pack, such as a notebook
computer, an improved system and method for controlling the output
voltage of the AC adapter and for obtaining information from the AC
adapter via a single wire interface is disclosed. More
specifically, the AC adapter includes AC line powered primary side
circuitry, such as a flyback converter, and secondary side
circuitry that generates a DC output voltage. First and second
control loops feed back an error signal through optical isolators
to the primary side circuirty to control the AC adapter output
voltage. The DC output voltage from the AC adapter is coupled to
the end equipment, such as a notebook computer and serves to power
the electronic device and to charge a battery pack that is
electrically coupled to the electronic device.
[0009] The interface between the AC adapter and the end equipment
includes two wires for coupling the positive and negative DC output
voltages to the end equipment. In addition, the interface between
the AC adapter and the end equipment includes a single wire that
serves as a control and data link. The control and data link
carries digital information when the AC adapter is in a first
operating mode and carries analog information when the AC adapter
is operating in a second operating mode.
[0010] In the first operating mode, a host within the end equipment
retrieves digital information from the AC adapter to identify the
AC adapter and/or an electrical characteristic pertaining to the AC
adapter. In the first operating mode, the AC adapter outputs a DC
voltage that is a percentage of the maximum DC output voltage of
the adapter.
[0011] In the second operating mode the end equipment controls an
analog error signal via the control and data link. The analog error
signal is applied to the primary side of the AC adapter to adjust
the primary side duty cycle of the input converter to control the
AC adapter output voltage. More specifically, in one embodiment,
the end equipment includes a current sink that sinks a current in a
closed loop with the AC adapter to control the AC adapter output
voltage. In the second operating mode, the AC adapter outputs the
maximum DC output voltage.
[0012] Additionally, a protocol provides for the transition between
the first and second operating modes to assure that the AC adapter
does not apply an excessive output voltage to the electronic device
which may cause damage to the circuitry within the battery-operated
device during power up or during use.
[0013] Other features, aspects, and advantages of the above
described system and method will be apparent to those of ordinary
skill of the art from the detailed description of the invention
that follows.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0014] The invention will be more fully understood by reference to
the following detailed description of the invention in conjunction
with the drawings of which:
[0015] FIG. 1 is a block diagram of a system, including an AC
adapter operative in accordance with the present invention;
[0016] FIG. 2 is a block diagram depicting the adapter of FIG. 1 in
greater detail;
[0017] FIG. 3 is a block diagram of end equipment cooperative with
the AC adapter of FIG. 2; and
[0018] FIG. 4 is a flow chart depicting the steps employed in the
use of a single wire to carry both digital information and analog
control signals.
DETAILED DESCRIPTION OF THE INVENTION
[0019] In accordance with the present invention, a method and
system for controlling the output voltage of an AC adapter and for
obtaining digital information identifying characteristics of the AC
adapter over a single wire coupling the AC adapter to end or
electronic equipment is disclosed.
[0020] Referring to FIG. 1, the system 100 includes an AC power
adapter 200, electronic equipment 300, such as a notebook computer,
and a battery pack 350. The AC adapter 200 generates positive and
negative voltage outputs which are couplable to the electronic
equipment 300 via an interface cable 102. The wires carrying the
positive and negative output voltages are identified as Adapter
Output+104 and Adapter Output-106 respectively.
[0021] Additionally, the interface cable between the AC adapter 200
and the electronic equipment 300 includes a control and data link
108. The use of the control and data link 108 is described in
greater detail below.
[0022] The electronic equipment 300 is also electrically coupled to
the battery pack 350 via a battery interface 110 as known in the
art. The battery pack 350 may include one or more rechargeable
batteries and serves to power the electronic equipment 300 when the
AC adapter 200 is not connected to the electronic equipment 300 or
not coupled to AC power via inputs 202. When the AC adapter 200 is
line powered and coupled to the electronic equipment 300 via the
interface cable 102, the AC adapter 200 powers the electronic
equipment 300 and charges the battery pack 350.
[0023] The AC adapter 200 and the electronic equipment 300
communicate cooperatively over the control and data link 108 in
first and second operating modes. More specifically, in the first
operating mode, also referred to herein as the digital mode, the AC
adapter 200 is configured to permit the electronic equipment 300 to
retrieve digital information from the AC adapter 200 serially over
the control and data link 108. The digital information may include
information identifying the AC adapter 200 or voltage or other
characteristics of the AC adapter 200. In the second operating
mode, also referred to herein as the analog mode, the control and
data link 108 is employed to carry an analog signal which is part
of a control loop. The analog signal is employed to generate an
error signal which controls the DC output voltage of the AC adapter
200. The analog signal is also employed to control transitions from
the analog mode to the digital mode as subsequently described in
greater detail.
[0024] One embodiment of an AC adapter 200 operative in accordance
with the present invention is depicted in FIG. 2. Referring to FIG.
2, the AC adapter 200 receives AC line power at AC inputs 202. The
AC line power is applied to a primary side converter 204 that is
responsive to an error signal 206 to modify the duty cycle of the
primary side waveform. The secondary side of the AC adapter input
circuitry includes first and second windings 208 and 210,
respectively that are coupled to rectifier diodes 212, 214 to
produce DC voltages VSense and Vcc. The signal VSense is coupled to
the adapter voltage output Adapter Output+ through a low pass
filter 216 comprising capacitors 216a, 216b and inductor 216c.
[0025] Resistors 218, 220 form a voltage divider which provides an
input voltage Vin to a first control loop that serves to control
the adapter output voltage. Vin is coupled to an attenuator 222.
The attenuator 222 is used to modify the first control loop so that
the adapter output voltage is set either to the maximum output
voltage for the AC adapter (in the analog mode) or an output
voltage that is less than the maximum output voltage by a
predetermined percentage (in the digital mode). The selection of
the specific attenuator characteristic occurs in response to a mode
selection signal 224 from AC adapter control logic 226. More
specifically, in one exemplary embodiment, the mode selection
signal 224 is asserted when the AC adapter is in the analog mode
and deasserted when the AC adapter is in the digital mode. The
attentuator 222 modifies the attentuator output 228 when the mode
selection signal 224 specifies the digital mode so that the first
control loop produces an error signal 206 that causes the AC
adapter output voltage to be set at a predetermined percentage of
the maximum output voltage. When the mode selection signal 224
specifies the analog mode, the attenuator 222 produces an output
signal 228 that causes the first control loop to produce an error
signal 206 that causes the AC adapter 200 to produce the maximum
specified output voltage.
[0026] The attenuator output signal 228 is coupled to the inverting
input of an operational amplifier 230. The non-inverting input of
the operational amplifier 230 is coupled to the output of a voltage
reference source 232. The operational amplifier 230 produces an
output signal 234 that is coupled to a first optical isolator 236.
The first optical isolator 232 is coupled to the error signal 206
which completes the first control loop. The high frequency gain of
the first control loop is controlled by a low pass filter 238 that
is coupled between the Vin input signal to the attenuator 222 and
the output signal 234 from the operational amplifier 230.
[0027] The AC adapter 200 further includes a communication engine
250 that is communicative to a memory 252. The communication engine
250 is cooperative with a host 302 in the electronic equipment 300
(see FIG. 3) to communicate digital information retrieved from the
memory 252 over the control and data link 108 to the host 302 when
the AC adapter is configured in the first or digital operating mode
as subsequently discussed in greater detail.
[0028] The AC adapter 200 also includes circuitry that is
cooperative with circuitry within the electronic equipment 300 to
form a second control loop to permit the AC adapter output voltage
to be controlled based upon commands sent from the end equipment
300. More specifically, when the AC adapter 200 is configured in
the second or analog operating mode, the control and data link 108
is employed to carry an analog control signal within the second
control loop.
[0029] The operation of the second control loop including the AC
power adapter and circuitry within the electronic equipment 300 is
further described in U.S. application Ser. No. 10/983,284, filed
Nov. 5, 2004, entitled Methods and Systems for Controlling an AC
adapter and Battery Charger in a Closed Loop Configuration, which
application is assigned to the same assignee as the present
application and is incorporated herein by reference.
[0030] An illustrative embodiment of the electronic equipment 300
is depicted in FIG. 3. Referring to FIG. 3 the electronic equipment
300 includes a current sink 304 that sinks current through the
control and data link 108 under the control of current sink control
circuitry 306.
[0031] As shown in FIG. 2, when the AC adapter is configured in the
analog mode and the control and data link 108 is carrying a control
current, the current passes through a resistor 260 and drives a
second optical isolator 262. The second optical isolator 262 is
coupled to the primary side 204 and controls the duty cycle of the
primary side converter in response to variations in the control
current sent from the electronic equipment 300.
[0032] The positive and negative outputs from the AC power adapter
200 are coupled to the DCIN+ and DCIN- inputs of the electronic
equipment 300 via the interface cable 102 (see FIG. 1). The DC
input voltage is coupled to the system electronics 320 and/or the
battery pack 350 during charging via the selection circuitry 330.
When the electronic equipment is being powered by the battery pack
350, the power is coupled to the system electronics via the
selection circuitry 330. The battery pack includes a number of
interface signals 110 that are coupled to battery interface
circuitry 352 within the electronic equipment 300 and monitored by
the host 302.
[0033] As shown in FIG. 2, the AC adapter 200 includes first and
second comparators 270, 272 that are used to determine whether the
control current through the control and data link 108 is above or
below predetermined current thresholds. More specifically, the
inverting input of the first comparator 270 is coupled to a
positive side of a voltage reference Vmax. The negative side of the
voltage reference is coupled a first end of the resistor 260. The
first end of the resistor 260 is also coupled to the control and
data link 108. The second end of the resistor 260 is coupled to the
non-inverting input of the first comparator 270. Consequently, when
the current passing through the control and data link 108 exceeds a
first predetermined current threshold, the output of the first
comparator 270 is asserted. The first comparator output signal is
coupled to the input of the control logic 226.
[0034] The second end of the resistor 260 is also coupled to the
non-inverting input of the second comparator 272. Additionally, a
positive side of a second voltage reference Vmin is coupled to the
inverting input of the second comparator 272. The output of the
second comparator is coupled to the control logic 226.
Consequently, when the current passing through the control and data
link decreases below a second predetermined current threshold, the
output of the second comparator 272 is asserted and conveyed to the
control logic 226.
[0035] As previously noted, the mode selection signal 224 specifies
whether the AC adapter is in the digital or analog mode. The AC
adapter 200 includes first and second switches 280 and 282 (see
FIG. 2) which are driven by opposite ends of an inverter 284. In
the first or digital operating mode, the second switch 282 is
closed and the first switch 280 is open. In this configuration the
communication engine is coupled to the control and data link 108
and the second control loop is disconnected. In the digital mode,
the communication engine can communicate with the host 302 (see
FIG. 3) over the data and control link 108. In the second or analog
operating mode, the first switch 280 is closed and the second
switch 282 is open. In this configuration, the second control loop
is operative and the communication engine output is disconnected
from the control and data link 108.
[0036] The operation of the disclosed system is further described
with respect to FIG. 2-4. As illustrated in step 400, the control
circuitry 226 is initialized on power up in the first operating
mode, i.e. the digital mode, in which the communication engine 250
is coupled to the electronic equipment 300 via the control and data
link 108. As depicted in step 402, the control logic 226 controls
the attenuator 222 so that the adapter output voltage is set at the
predetermined percentage of the maximum specified adapter output
voltage. In this manner, the voltage applied to the electronic
equipment 300 is limited to a voltage that will not cause any harm
to the circuitry within the electronic equipment 300 due to an
overvoltage condition.
[0037] As depicted in step 404, the host 302 next accesses the
digital information stored in the memory 252 via the communication
engine 250 over the control and data link 108. The information may
be forwarded by the communication engine 250 in response to a
command from the host 302 or at the initiation of the control logic
226. The host 302 next determines if the information has been
received and if the information indicates that the AC adapter 200
is a valid adapter, as illustrated in decision step 406. In the
event the host 302 determines that the attached adapter is a valid
adapter, the host 302 transmits a command to the communication
engine 250 that indicates that the adapter has been determined to
be valid, as illustrated in step 408. In response to the receipt of
the indication that the AC adapter has been determined by the host
302 to be a valid adapter, the communication engine 250 signals the
control logic 226. In response to receipt of the signal at the
control logic 226 indicating that the AC adapter is valid, the AC
adapter 200 switches to the second operating or analog mode in
which the current sink 304 sinks current over the control and data
link 108 from the AC power adapter 200 as illustrated in step 410.
In this mode the second control loop is operative to control the
output voltage of the AC adapter based on the voltage sensed at
DCIN+. As depicted in step 412, in the analog mode, the AC adapter
output voltage is clamped by the adapter control loop to the
maximum adapter output voltage.
[0038] The AC adapter remains in the second operating mode until
either the first or second comparator output indicates that the
control logic should transition to the digital mode. As previously
discussed, if the current level through the control and data link
108 exceeds a first predetermined current level, as sensed by the
first comparator 270, the AC adapter 200 reverts to the digital
mode. Additionally, if the current level in the control and data
link 108 goes below a second predetermined current level which is
less than the first predetermined current level, as sensed by the
second comparator 272, the AC adapter 200 reverts to the digital
mode. The detection of a current level in the control and data link
108 below the second predetermined level indicates that the
electronic equipment 300 has been disconnected from the AC adapter
200.
[0039] In the foregoing manner, the control and data link 108
between the AC adapter 200 and the electronic equipment 300 may be
employed to convey both digital information used by the electronic
equipment to validate the AC adapter and to convey an analog signal
forming a part of the second control loop.
[0040] It will be appreciated by those of ordinary skill in the art
that the host may be implemented as a microprocessor, a controller,
hardware logic, or any suitable combination of hardware and
software operative to perform the functions herein described.
[0041] Furthermore, while the control signal passed through the
control and data link 108 is described as a current in the
illustrated embodiment, it will be appreciated that the control
signal may be implemented as a varying analog voltage.
[0042] Finally, it will be appreciated that modifications to and
variations of the above-described apparatus and method may be made
without departing from the inventive concepts disclosed herein.
Accordingly, the invention should not be viewed as limited except
by the scope and spirit of the appended claims.
* * * * *